It's not the steel (iron) rotors, but the hubs which are made of aluminum instead of cast iron that save the weight in most systems. You want a system with "floating hat" rotors. Also, I believe one of the Brembo kits, perhaps the 8-piston caliper upgrade, is made with some titanium so that it actually weighs less than the 6-piston calipers.

 

From what I hear the titanium part is only a very minor weight savings. Unfortunately I can't quantify it for you.

Here's a question for you. On the 15" kit, I was told that you do NOT have to replace the hubs. But, still, there's a significant weight savings. On the 14" kit, I was told that you DO have to replace the hubs. Is this all true? If so, wouldn't the 14" kit be much, much lighter?

-Donn

 

Not sure what kits we talking about here...There are 2 8-piston kits for the 996TT from brembo. One is the Le Mans kit (big $$) the other is the Gran Turismo kit. I have the gran turismo kit and if you check my sig there are pictures of all the parts. I have 15" 2-piece floating front rotors and 14" two-piece floating rear rotors. The front calipers are the monstrous 8-pistons whlie the rear are a nw 4-piston.
I think the weight of this system is less than the stock one...

 

Mansour -

Did they come with different hubs? Or did the rotors bolt onto the existing Porsche hubs?

-Donn

 

bolt on the existing hubs...

 

just confused myself (do that a lot). don't the 996 c2 and first gen gt3 use the same sized and spec tires (contact patches)? if so and since the c2 and gt3 weigh about the same, how come porsche uses the tt brakes on the gt3 if somehow bigger doesn't do "something". what is that something?

 

Donn -- Call Barry Borin at Race Technologies (Brembo distributors and brake specialists) -- 310-306-3158, ext 23 -- he knows brakes. He can answer all your questions.

Brembo does make a 2-piece floating hat rotor for the 360 which utilizes the stock calipers. The weight savings was 6 lbs per corner. When I last checked to see if they had the same type of product for a 996TT, the answer was no.

Here's a photo of the 360 2-piece "challenge style" floating hat rotor

 

I used to know this stuff, but the last time I did the research was several years ago... and I can't remember it all right now. Worse yet, my bible on brakes (the book by Fred Puhn) is at home. But, if I'm remembering things correctly, a larger rotor surface area dissipates heat better relative to a smaller surface area. So, on a race track, there is a lower probability of fade. Rotor thickness also helps dissipate heat as well. Other things equal, thicker is better.

Also, I beleive that greater pad surface area can reduce braking times due to increased friction (relative to a smaller pad)... Someone please correct me if I'm wrong on that one...

 

Thanks Jack!

 

"Donn -- Call Barry Borin at Race Technologies (Brembo distributors and brake specialists) -- 310-306-3158, ext 23 -- he knows brakes. He can answer all your questions.

Brembo does make a 2-piece floating hat rotor for the 360 which utilizes the stock calipers. The weight savings was 6 lbs per corner. When I last checked to see if they had the same type of product for a 996TT, the answer was no."

I talked to Race Technologies a couple weeks ago and at that time the answer was still no.

 

Guys,

Brakes are a big and complex subject. One thing I want to point out. I don't believe stopping faster will benefit to any noticable degree. If you have had overheating issues, you should first go after imporved cooling, then to bigger brakes.

Now, if you are after unsprung weight, lighter hats, and expecially rotors (rotating mass) can help. If you go with lighter rotors, you have to be careful that they can absorb the transient heat loads. Your handling is almost always improved with lower unsprung weight, but can propably be improved even further by slight suspension tuning to re-optimize the system afet the weight reduction.

If you change the caliper piston area, you should try to find someone who can tell you if the ABS system will be affected. It is tuned for a certain hydraulic movement and this will change with different pistion areas. I am not an ABS expert so I don't know how sensitive they are.

I really don't think bigger pistions will help the brakes much. Maybe larger pad area and heat absorption, maybe somewhat quieter (less pad shudder), but these are probably pretty minor factors. Again, I haven't tracked my car yoet so I can't say this with confidence yet.

 

I think after reading this thread I must have the 15" 8 piston Gran Turisimo kit. They work fine with the 18" Fikses as I have noted. I have zero experience with the car with stock brakes, so I cannot comment on that. However, and this is just my speculation, it is not so much a reduction in one-stop performance but rather the ongoing performance during a sustained session on a twisty road. Further I think the biggest advantages of the upgrade are not only the better resistance to fade, but the much higher braking torque that the larger rotor gives.

 

John, this is the classic mistake most people make about brakes. Your Porsche is not brake torque limited, it is tire traction limited. IF your brakes actuate the ABS system, further force and torque is unnecessary!

Now, heat handling, unsprung weight, ... can be better, BUT NOT STOPPING POWER. Only the tires can improve stopping power once your able to reach threshold braking (or ABS).

 

Ahhh. Finally. My memories from the Puhn book are coming back to me. Unfortunately, racing in classes that required me to run stock brakes (with only ducting, race pads and stainless lines available to upgrade) my once reasonably solid brake knowledge faded as quickly as a set of stock Camry pads at the old Holtville Airport race circuit.

Thanks Tim for the refresher. Now if I can just find where I put that Puhn book for reading over the weekend during my San Diego get away...

 

One other data point the hopefully will help is the Autothority 750 HP monster that was built for the Car & Driver Super Tuner Challenge. In any case, one of the test was a 150-0 braking competition. After spending $50K+ on all other stuff, they left the brakes stock. I do not see it mentioned but I remember the article correctly, they only changed the pads (which one, I do not remember).

http://www.autothority.com/news/super_tuner.htm